# C44 calculation by E vs strain for cubic crystal

Dear LAMMPS users,
I am trying to calculate C44 elastic constant for a cubic single crystal from energy vs lattice distortion curve.
For that the strain matrix I am using is:
(0 x 0)
(x 0 0)

(0 0 x^2/1-x^2).
This strain is making cubic lattice into a monoclinic one with alpha=90 degree,beta=90 and gamma=93.4367.

For x= - 0.03 input file is written below:
I have calculated tilt factors based on relations
xy= b cosγ = −0.328198474
xz=c
cosβ= 0
yz = bc cosα- xyxz/Ly = 0
lx=a=5.474923
ly^2=b^2-xy^2=29.867067618
ly=5.465077092
lz^2=c^2-xz^2-yz^2
lz=5.474927435

Dear LAMMPS users,
I am trying to calculate C44 elastic constant for a cubic single crystal
from energy vs lattice distortion curve.

[...]

In the process of simulation 2085 atoms were generated which is not a
multiple of 12. So i am getting a energy value with this setting far away
from energy minima and even more negative cohesive enegy than eqillibrium
lattice. And this is also true for other values of x. Off course this is
because my system is not charge neutral so many things are going wrong.
So, could any one please help me out to solve this isssue.

shift your system cell a little bit, so its boundaries don't coincide
with the lattice points and whether an atom is inside or outside the
box is no longer subject to floating point truncation errors.

axel.